Accurate Bias Stress Instability Measurements in High-Performance ITO FETs Using Modified On-the-Fly Technique

We report on Indium Tin Oxide (ITO) dual-gated field-effect transistors (DG-FETs) achieving a high ION of 1.2 mA/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m at a gate overdrive, VOV of 2.5 V, with a top-gate effective oxide thickness of 0.85 nm. When stressed with VOV = 3.5 V, the devices exhibit ultralow threshold voltage shift (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula>Vth) of just 19 mV, as measured by the conventional measure-stress-measure (MSM) technique commonly used in the amorphous oxide semiconductor (AOS) community. However, employing a modified on-the-fly (OTF) method for reliability testing reveals a 500% increase in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula>Vth for the same ITO device, due to the Vth recovery occurring within milliseconds after stress is removed. This substantial difference, also observed in multiple devices, highlights the possible underreporting of threshold shifts in the MSM method due to fast Vth recovery. Thus, our results underscore the importance of recovery-analysis for reliability study of AOS devices and choosing OTF method for devices with fast recovery. Our study establishes a robust framework for measuring and understanding the root causes of Vth instabilities in ITO transistors.